The present invention relates to apparatus and methods for transferring control from one control unit of a multi-variable control unit to another and more particularly to apparatus and methods for transferring control which include intercommunication between control units of a multi-variable control unit, that is, a unit processing many variables.
Prior art has disclosed several systems for transferring control from one control unit to another control unit. Most of these transfer systems are manual, that is, when one control unit ceased to function, a technician would manually transfer control from one unit to a back-up unit. Prior art has also disclosed a sophisticated automatic transfer system wherein the back-up controller monitors the primary controller and automatically initiates transfer whenever the primary controller performs a function with which the back-up controller does not agree.
The deficiency of manual control systems is that it is unreliable, requiring both the presence and alertness of a technician to manually transfer control from one controller to another. Although the technician may be extremely reliable, a complex system requires close evaluation of several variables which will divide his or her attention. Sophisticated automatic transfer systems have their deficiency in the complexity of circuitry involved and in the fact that when transfer is initiated due to a disagreement between controllers, the differences between the back-up controller calculations and the primary controller calculations could be due to circuit imbalances as well as a faulty primary controller. In addition, the back-up controller may be incorrectly calculating values due to its own component failure. The two systems, although identical in component content, may nevertheless be imbalanced due to manufacturing inequalities of the components. While any imbalance may not be apparent in macroscopic calculations, it may show up in microscopic calculations. This detracts from the overall system accuracy since percentage errors must be permitted to prevent "false" or unnecessary transfers.
It is therefore an object of the present invention to provide a reliable automatic transfer system and apparatus.
It is also an object of the present invention to provide an automatic transfer system which requires no complex circuitry.
It is a further object of the present invention to provide an inexpensive automatic transfer system.